小麦哲伦云同步辐射信号与暗物质湮灭信号的研究

Study on Synchrotron Radiation Signal and Dark Matter Annihilation Signal in Small Magellanic Cloud

摘要: 高能正负电子在磁场中损失能量产生同步辐射信号，在不规则矮星系中，暗物质自湮灭和宇宙射线均能提供高能正负电子。在本篇文章中，我们拟重新分析近邻不规则矮星系，小麦哲云中的同步辐射信号，比较了考虑宇宙射线贡献和扣除宇宙射线贡献，对暗物质质量的限制。我们首先假定所有的同步辐射信号由暗物质湮灭产生，在给定热遗迹湮灭截面下，对三种不同的典型暗物质湮灭道下拟合观测数据对暗物质粒子质量的限制。我们发现 湮灭道给出最佳的谱形拟合。进一步，我们通过射电红外关联计算由宇宙射线产生的同步辐射信号，将探测到的流量减掉这部分的贡献，剩下的部分作为暗物质自湮灭产生的上限。同样考虑 湮灭道，我们通过调整暗物质粒子质量拟合数据，给出两种磁场假定下，最佳拟合对应的暗物质质量。我们发现在合理地扣除宇宙射线贡献的情况下，同样的热遗迹截面，限制的暗物质粒子质量更大。磁场更大时，对应暗物质粒子质量的上限更大，对谱线的整体拟合更好。

Abstract: High-energy positrons and electrons lose energy in the magnetic field to produce synchrotron radia-tion signals. In irregular dwarf galaxies, both dark matter self-annihilation and cosmic rays produce high-energy positrons and electrons. In this paper, we review the synchrotron radiation signals in the Small Magellanic Cloud, an irregular dwarf galaxy in the neighborhood, and compare the con-straints on dark matter mass with and without cosmic ray contributions. We first assume that all the synchrotron radiation signals are generated by dark matter annihilation. Given the thermal relic annihilation cross section, the mass constraints on dark matter particles are limited by fitting observed data under the assumption of three different typical dark matter annihilation channels and we find is the best annihilation channel to fit the spectrum shape. Furthermore, we calculate the synchrotron radiation signal generated by cosmic rays through radio-infrared correlation, subtracting the contribution of this part of the detected flux and using the remaining part as the upper limit from the self-annihilation of dark matter. Taking into account annihilation channel, we give the corresponding dark matter mass under the two magnetic field assumptions by adjusting the dark matter mass to fit the data. When the contribution of cosmic rays is reasonably deducted, the upper mass of dark matter particles allowed is larger than that obtained without cosmic ray contribution subtracted at the same thermal annihilation cross-section.